Light intensity adjusting system

ABSTRACT

A light intensity adjustment system is provided which greatly decreases or makes unnecessary image compensation by the image processing device side, improves scan precision, and can reduce the scan time; and which comprises: a light irradiation device  1  that has multiple independently light intensity adjustable light irradiation units  11 , and that irradiates light facing a predetermined target area A; a photographic device  2  that photographs said target area A through a lens, and outputs a target area image that is the photographed image; and a light intensity control unit  3  that controls the respective light intensities of said light irradiation units  11  so that the brightness of the various parts of the target area images that said photographic device  2  has output approaches a predetermined standard value.

TECHNICAL FIELD

The present invention is related to a light intensity adjustment systemfor adjusting the light intensity to irradiate when conducting externalappearance scans and defect scans by photographing the target area of awork piece.

BACKGROUND ART

In the past, when conducting inline high-speed scans of WEB (continuousobjects: film, paper, sheet metal) and BATCH (sheet products, individualproducts: cut film, cut glass, drums), which are the objects to bescanned, scans for surface defects were conducted by using line sensorcameras, incorporating the surface of the flowing work pieces ascontinuous image data, and, with an image data processor, detectingareas that differ in brightness.

At that time, in order to precisely detect surface faults, it wasnecessary to illuminate uniformly with a fixed illumination intensitythe area targeted for photography by said camera, and conventionallyhalogen lamps and fluorescent lights were used as the light irradiationdevices for this purpose. Moreover, devices using LEDs that are superiorin velocity responsiveness, stability of light intensity, and lifetime,etc. have recently been developed as a substitute for these lightsources.

In this regard, even though illumined uniformly without unevenness onthe area targeted for photography, the brightness level of thephotographed image is higher in the central part and increasingly lowertoward the edges because of lens aberration (distortion), or differencesin the distance between the camera and the parts of the area targetedfor photography or differences of image angle. In particular, thistendency is notable if using a wide-angle lens. Concretely, indicated inFIG. 15 is a depiction of video signals (signals of light received by acamera (CCD) converted to electronic signals), which are output from acamera.

Thus, in the past, after incorporating the image signals from thecamera, the brightness of these signals was adjusted (shadingcompensation) on the image processor side by compensating on the signallevel, for example, digitally, and scan processing was conductedthereafter. Typically, there are addition and subtraction devices thatadd brightness that is lacking to dark areas of the incorporated imagethat should have a fixed level of brightness, and subtract brightnessfrom parts that are too bright; and there are devices that compensatethe brightness of the various parts to a fixed level by gain control(multiplication). Further, there are a variety of methods that form thebasis of compensation in these methods, as represented by PatentLiterature (Japanese Unexamined Patent Application Publication No.H10-111251).

Nonetheless, when conducting shading compensation on the image processorside, there is the risk that image deterioration when converting thedigital signals and differences in the calculation method duringcompensation may have a deleterious effect on the precision of detectingdefects, etc. This will be explained by citing specific examples.

As indicated in FIG. 24, for example, the central part and the edge partin the width direction respectively have the same defect. Nonetheless,the brightness level that is entered as a signal for the defect at theedge is smaller because of the darkness.

When, for example, shading compensation is conducted from the imageprocessor side with said addition and subtraction making the brightnesslevels of the whole uniform, as indicated in FIG. 25, a difference inthose brightness levels may be generated because only the background iscompensated and no changes are generated in the relative level of thedefect from the background, irrespective of the central part and theedge having the same defect, and thus there is the specific risk ofvariance in the detection of defects. For example, if the thresholdlevel of defect detection were set at the dotted line in this diagram,the defect on the edge would not be detected.

Meanwhile, if shading compensation is conducted from the image processorside with said gain control (multiplication) making the brightnesslevels of the whole uniform, as indicated in FIG. 26, the defect levelsof the central part and the edge are uniform because both the backgroundand the defect levels are compensated. However, gain control alsoamplifies noise near the edge, and produces the risk of mistakenlydetecting this noise as a defect. For example, if the threshold level ofdefect detection were set at the dotted line in this diagram, the noisewould be detected as a defect.

Further, because the load on the image processing side becomes larger,there is a resulting disadvantage that the scan time cannot be shortenedwithout shortening the image processing time; and there is also thedisadvantage that costs will increase if the scale of the imageprocessor is increased. Moreover, there are devices that conduct thesame kind of shading compensation on the photographic equipment side,but the same kinds of image deterioration, etc. can occur.

DISCLOSURE OF THE INVENTION

Thus, the present invention is a device that attempts to change theapproach and control the light irradiation device such that, when thecamera incorporates the image, for example, the brightness of the targetarea of that image is made uniform, or unevenness is positivelygenerated; and by greatly reducing or making unnecessary the imagecompensation processing by the image processor side, addresses theproblems of interest, namely, to improve scan precision by preventingfalse detection that can be generated when conducting compensationprocessing on that image; and to shorten scan time.

Specifically, the present invention is a light intensity adjustmentsystem that comprises: a light irradiation device that provides multiplelight irradiation units that are independently light intensityadjustable, and that irradiate light toward predetermined target areas;a photographic device that photographs said target areas through a lens,and outputs target area images that are the photographed images; and alight intensity control unit that controls the respective lightintensities of said light irradiation units so that the brightness ofthe various parts of the target area images that said photographicdevice has output approaches a predetermined standard value.

More concretely, the present invention comprises: a light irradiationdevice that irradiates light on a predetermined target area set up on awork piece; and a photographic device that photographs that target area,and outputs the obtained target area images to an image processor forthe purpose of a surface scan; characterized in that: said lightirradiation device has multiple light irradiation units that areindependently light intensity adjustable; and a light intensity controlunit is further provided to control the respective light intensities ofsaid light irradiation units so that the brightness of the various partsof the target area images that said photographic device has outputapproaches a predetermined standard value.

With this kind of device it is possible to prevent diminishing scanprecision caused by image deterioration when compensating because it ispossible to greatly reduce or make unnecessary image compensationprocessing, such as shading compensation by the image processor side. Inaddition is becomes possible to broadly promote shortening scan time andimproving scan precision because the image processing device canconcentrate on the original image processing necessary for scanning.

Here, the various light irradiation units may be light emitting bodiessuch as one or multiple LEDs, etc., or the light exit end of a lightguide such as optical fibers. If using a light guide, separate lightemitting bodies are necessary.

When using to scan for defects, it is preferable to control the lightintensities of the various light irradiation parts oriented towardmaking the brightness of the various parts of said target area imagesuniform.

Slight differences in the respective light intensities and irradiationangles caused by fluctuations of product quality and mounting errors,etc. can occur in the light irradiation units. In relation to this,there is the risk that the device may become inadequate from theperspective of control speed and control error, etc. because eachirradiation unit is controlled in the same way. To suitably resolve thisproblem, it is preferable to further comprise an individual lightirradiation aspect data memory unit, whereby light irradiation aspectson said target area based on the light irradiated from the individuallight irradiation units are acquired in advance from said target areaimages and are memorized as individual light irradiation aspect data;and to provide a configuration that controls the light intensities ofsaid light irradiation units based on said individual light irradiationaspect data.

Data that at least indicates the light irradiation range and brightnessdistribution on the target area by the various light irradiation unitsthat are supplied a predetermined power may be cited as concretecontents of said individual light irradiation aspect data.

Attempting to simplify control, it is preferable to divide said targetarea into multiple unit areas, to make one light irradiation unit mainlyirradiate a unit area corresponding to the unit area in question, and tomake that light irradiation unit be the main light irradiation unit ofthe unit area in question. In this way if only the main lightirradiation unit controls the brightness of one unit area, lightintensity control is simplified.

Concretely, it is preferable that there be a one to one correspondencebetween said unit areas and the light irradiation units.

Dividing said target area into multiple unit areas so that the number ortype of light irradiation units that irradiate the unit areas with lightrespectively differ based on the range of light irradiation of thevarious light irradiation units indicated by said individual lightirradiation aspect data may be cited as a method of division into unitareas. Moreover, in this case, the light irradiation unit that gives themost light intensity to the various unit areas may be taken as the mainlight irradiation unit of the unit area in question based on thebrightness distribution of the various light irradiation units indicatedby said individual light irradiation aspect data.

A preferable concrete form of realizing this may include a devicewherein said light intensity control unit comprises: an image separationunit that separates said target area image into images of said unitareas; a representative value calculation unit that calculates therepresentative value of the brightness of the unit area images; acomparison unit that compares the representative values of said unitarea images with a predetermined standard value of the brightness; and aunit light intensity control unit that controls the light intensity ofthe main light irradiation unit corresponding to the unit area inquestion, such that the various representative values approach saidstandard value based on the results of comparisons by said comparisonunit.

The mean brightness of the unit area image is preferable as therepresentative value in this case.

If the scan object is a WEB, then a light irradiation device that linesup the light irradiation units in a linear shape is preferable, but whena BATCH, a light irradiation device that lines up the irradiation unitsin the surface shape is acceptable. Here, the meaning of surface is notlimited to planar, and also includes curved surfaces.

Preferably, the light irradiation device comprises a light intensityunevenness-mitigating member that mitigates light intensity unevennessdependent on the gaps between adjacent light irradiation units. In lineillumination, a lenticular lens that diffuses the light only in a fixeddirection may be cited as this light intensity unevenness-mitigatingmember, and in surface illumination, a light diffusion plate may becited.

Moreover, if multiple photographic devices are comprised and said targetarea is photographed by dividing said target area based on thesephotographic devices, overlapping photographs of a part of said targetarea by adjacent photographic devices may occur. In this case, there isthe problem of which image of the overlapping area obtained from thephotographic devices is to form the basis for controlling the lightintensity. In this case, for overlapping target areas, it is preferableto control the light intensity of the corresponding light irradiationunit based on the image obtained by the photographic device with thehigher priority ranking, and for the target area that the photographicdevice with the lower priority ranking photographs, the light intensityof the light irradiation unit corresponding to the other area iscontrolled taking the image of the previously described overlapping areaas a standard.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall conceptual configuration diagram of a lightintensity adjustment system of the first embodiment of the presentinvention.

FIG. 2 is a partial cut-away perspective view diagram of a lightirradiation device of the same embodiment.

FIG. 3 is an perspective view diagram indicating a holder of the sameembodiment.

FIG. 4 is a functional block diagram of the light intensity control unitof the same embodiment.

FIG. 5 is a flow chart indicating the operation of a light intensitycontrol unit of the same embodiment.

FIG. 6 is a signal diagram indicating the image signals prior to lightintensity compensation in the same embodiment.

FIG. 7 is a signal diagram indicating the light intensity compensationtarget of the same embodiment.

FIG. 8 is a functional block diagram of a light intensity control unitof a second embodiment of the present invention.

FIG. 9 is a data distribution chart graphically indicating thebrightness distribution data of the same embodiment.

FIG. 10 is an explanatory diagram indicating a graph to explain theprocess of setting the central position of the light irradiation unit ofthe same embodiment.

FIG. 11 is an explanatory diagram indicating a graph to explain theprocess of setting the irradiation range of the light irradiation unitof the same embodiment.

FIG. 12 is a data distribution chart using a bar graph to indicate thebrightness specific distribution data of the same embodiment.

FIG. 13 is a pattern diagram indicating the method to set the unit areasof the same embodiment.

FIG. 14 is a flowchart indicating the operation of the light intensitycontrol unit of the same embodiment.

FIG. 15 is a flowchart indicating the operation of the light intensitycontrol unit of the same embodiment.

FIG. 16 is a frame format data structure diagram indicating thestructure of the individual light irradiation aspect data of the sameembodiment.

FIG. 17 is a pattern diagram indicating a photographic device of anotherembodiment of the present invention.

FIG. 18 is a control explanatory diagram for explaining the lightintensity control of the same embodiment.

FIG. 19 is a control explanatory diagram for explaining another lightintensity control of the same embodiment.

FIG. 20 is a pattern diagram indicating a light irradiation device ofanother embodiment of the present invention.

FIG. 21 is a target area diagram indicating the form of dividing thetarget area in another embodiment of the present invention.

FIG. 22 is a target area diagram indicating the form of dividing thetarget area in another embodiment of the present invention.

FIG. 23 is a partial cut-away perspective view diagram of a lightirradiation device of another embodiment of the present invention.

FIG. 24 is a signal diagram indicating a conventional image signal.

FIG. 25 is a signal diagram when adding image processing to aconventional image signal.

FIG. 26 is a signal diagram when adding image processing to aconventional image signal.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be explained below byreferring to the diagrams.

First Embodiment

FIG. 1 indicates an overall summary of a light intensity control systemrelated to the present embodiment. This light intensity control systemis, for example, used in a surface scan of a product, etc.; the scanobject (work piece) W of the present invention is, for example, acontinuous object such as translucent paper or film; and is set up toflow in a predetermined direction at a fixed speed.

Accordingly, as indicated in the same diagram, this light intensitycontrol system comprises: a light irradiation device 1 that has multipleindependently light intensity adjustable light irradiation units 11, andirradiates light toward the back surface predetermined region of saidwork piece W; a photographic device 2 that photographs the lightirradiated predetermined target area A from the front surface through alens not indicated in the diagram, and outputs target area images, whichare the photographed images; and a light intensity control unit 3 thatcontrols the respective light intensities of said light irradiationunits 11 so that the brightness of the various parts of the target areaimages that said photographic device 2 outputs approach a standardvalue.

The various parts will be described in detail.

As indicated in FIG. 2 and FIG. 3, the light irradiation device 1comprises: multiple power LEDs 5 that are light emitting bodies; opticalfibers 6 that are flexible light guides that lead the light exiting fromthe various power LEDs 5; and a casing 7 that supports the light exitingend of the optical fibers 6.

The multiple optical fibers 6 are respectively connected to the powerLEDs 5, and said casing 7 comprises multiple holders 71 that support thelight exiting end of a group of optical fibers 6 connected to thesepower LEDs 5, and a casing main body 72 that supports these holders 71in a row to be orthogonal to the direction of flow of said work piece W.The light exiting ends of said group of optical fibers 6 are supportedin a line and in the same direction by one holder 71, and configure onelight irradiation unit 11 having a linear shape. Further, the opticalfibers 6 are pinched in the holder 71, and, for example, are fixed withan adhesive.

Then, the light emitted from the various light irradiation units 11irradiate at a nearly one to one correspondence in multiple unit areasUA, into which said target area A is divided, and as a whole makes acontinuous line of illumination of a predetermined width. Moreover, apair of refractive lenses 73 (Fresnel lenses), which refract the linearshaped light exiting from said light irradiation units 11 so that thewidth is narrowed, are mounted in said casing 7. The holder 71 isconfigured to be position changeable in relation to the casing main body72 by loosening and tightening a screw N. By modifying the distancebetween the light irradiation units 11 and the lens 73, the angle atwhich the exiting light is brought together can be changed. Further, thepower LEDs 5 are ultra-high brightness LEDs, each of which has a currentof approximately 200 mA when connected in a single unit.

The photographic device 2 is, for example, called a line sensor camera,and has CCD elements lined up in one row. Then, the light exiting fromsaid predetermined region is focused on the light receiving surfaces ofthese CCD elements through, for example, a wide angle lens, notindicated in the drawing, provided in this photographic device 2; thisincident light is converted to electric signals, and is output as imagesignals that can be processed as an image. As indicated in FIG. 4, theseimage signals are transmitted to an image processing device for surfacescanning, and in parallel with this, the image signals are alsotransmitted to the light intensity control unit 3 that will be describedlater.

The light intensity control unit 3 is connected to the various powerLEDs 5 through a current cable CA, and controls the current provided tothese, and also serves as the power source of the light irradiationdevice 1. This light intensity control unit 3 is a separate unit fromsaid light irradiation device 1, and as indicated in the functionalblock diagram in FIG. 4, comprises: a power source 35; an imageseparation unit 31 that separates said image signals into unit areaimage signals for every unit area UA; representative value calculationunits 32 that calculate from these signals the representative value ofthe brightness (luminance level) of the various unit area images;comparison units 33 that compare the representative values of thevarious unit area images with a predetermined standard value ofbrightness; and current control units 34 that are unit light intensitycontrol unit to control the supply current to the corresponding powerLEDs 5 such that the various representative values approach saidstandard value based on the results of comparisons by said comparisonunits 33. The functions as these units are manifested by operating a CPUor its peripheral devices in accordance with a program memorized inmemory not indicated in the diagram, or by operating a discrete circuitsuch as an analogue amplifier, etc. Further, in this embodiment, saidrepresentative value is the average value of the brightness of said unitarea images. This is because the signal strengths may be simplyintegrated.

One example of the operation of a light intensity adjustment systemrelated to the present embodiment configured in this way will beexplained below by referring to FIGS. 5 to 7.

(1) Light Intensity Adjustment Operation

First, the standard value of brightness of the target area image is setup. Here, this is a fixed value. Next, in the state without the workpiece, or in the state of a work piece with no defects, etc. installed,the light irradiation device 1, the light intensity control unit 3, andthe photographic device 2 are operated.

Then, the photographic device 2 first photographs the target area A(FIG. 5 step ST1), and the target area image is transmitted to the lightintensity control unit 3 as image signals (FIG. 5 step ST2).

At the light intensity control unit 3, as indicated in FIG. 6 and FIG.7, said image signals are divided into the unit area image signals ofeach unit area UA (FIG. 5 step ST3), and the representative value of thebrightness (luminance level) of the various unit area images iscalculated from these signals (FIG. 5 step ST4). Then, the predeterminedstandard value of brightness and the representative value of said unitarea images are compared, the supply currents to the corresponding powerLEDs 5 are controlled based on these comparison results such that thevarious representative values approach said standard value (FIG. 5 stepsST6 to ST8). An FB loop is formed in this way, and the light intensityof the light irradiation device 1 is adjusted until finally thebrightness of the various units of the target area image are within thepermissible range in relation to the standard value (FIG. 5 step ST5).

(2) Operation of Scan Illumination

In the present embodiment, after adjusting the light intensity of thelight irradiation device 1 in this way, specifically, after teaching iscompleted, the light intensity of the light irradiation device 1 isfixed, and scanning of the surface of the work piece will be conductedat that light intensity.

Consequently, according to the present embodiment, diminishing scanprecision caused by image deterioration, etc. when compensating can beprevented because image compensation such as shading compensation, etc.by the image processor side is greatly reduced or made unnecessary. Inaddition, shortening scan time and improving the scan precision can bebroadly promoted because the image processor can concentrate on theimage processing necessary for the original scan.

Moreover, said target area A is divided into multiple unit areas UA, a 1to 1 correspondence is set up between the various unit areas UA and thelight irradiation units 11, and the light of the light irradiation units11 mainly irradiate the corresponding unit areas UA. Therefore, whencontrolling the light intensity, it is clear which light irradiationunit 11 should be controlled, and the control method may be simplified.

Second Embodiment

Next, a second embodiment of the present invention will be explainedbased on the diagrams. Further, in the following explanation the samecodes will be used for members that correspond to those of said firstembodiment.

The light irradiation system of this second embodiment has nearly thesame configuration as that of said first embodiment. However, there is aslight difference in the configuration of the functions of the lightintensity control unit 3. The explanation below will concentrate on thepoints of difference from the first embodiment, and an explanation ofcommon points will be omitted.

The light intensity control unit 3 of this embodiment is connected tothe various power LEDs 5 through current cable CA, and controls thecurrent supplied to these. As indicated in the functional block diagramin FIG. 8, comprises: a power source 35; an image separation unit 31that separates said image signals into unit area image signals for everyunit area UA; representative value calculation units 32 that calculatefrom these signals the representative value of the brightness (luminancelevel) of the various unit area images; comparison units 33 that comparethe representative values of the various unit area images with apredetermined standard value of brightness; and current control units 34that are unit light intensity control unit to control the supply currentto the corresponding power LEDs 5 such that the various representativevalues approach said standard value based on the results of comparisonsby said comparison units 33. These units are the same as in embodiment1.

Accordingly, in addition to said configurational elements, the lightintensity control unit 3 of this second embodiment further comprises: anindividual light irradiation aspect data acquisition unit 36 thatacquires in advance light irradiation aspects on said target area Abased on the light irradiation from the individual light irradiationunits 11 as individual light irradiation aspect data from said targetarea images; unit area division unit 37 that divides said target area Ainto multiple unit areas UA based on the range of light irradiation bythe various light irradiation units 11 that said individual lightirradiation aspect data indicates; and a correspondence setting unit 38that sets a correspondence between each unit area UA and the one lightirradiation unit 11 that mainly irradiates that area, and that lightirradiation unit 11 is taken as the main light irradiation unit 11 ofthe unit area UA in question.

Combined with a detailed explanation of each of said parts, an exampleof operating the light intensity adjustment system configured in thisway will be explained below.

(1) Initial Adjustment Operation

First, the individual light irradiation aspect data acquisition unit 36acquires in advance the light irradiation aspect on said target area Afrom said target area image as individual light irradiation aspect databased on the light irradiation from the light irradiation units 11 (FIG.14 steps ST11 to ST19).

Concretely, light is first irradiated from one suitably set lightirradiation unit 1. The supply power level is in multiple stages, andhere for example, it is in three stages. Then, every time a lightirradiation unit 11 is lit at each stage, the target area A isphotographed by the photographic device 2, and the brightnessdistribution data (indicated by the graph in FIG. 9) on the target areaA for each of said supply power levels is incorporated from that imagedata. The incorporated brightness distribution data includes acorrelation between position data and brightness data, and is memorizedin a predetermined region of memory. This is conducted for all lightirradiation units 11 in order.

Next, as indicated by the graph in FIG. 10, the maximum value of thebrightness and that position are specified from said brightnessdistribution data, and this is taken as the illumination centralposition of the light irradiation unit 11 in question (FIG. 15 stepST21). Moreover, as indicated by the graph in FIG. 1, the bright part isspecified by a predetermined brightness, and that range is taken to bethe irradiation range of the light irradiation unit 11 in question (FIG.15 step ST22).

Meanwhile, if, for example, said maximum brightness value is set at 100,then brightness ratio distribution data indicating the distribution ofthe brightness ratio to that is produced at every power level from saidbrightness distribution data (FIG. 15 step ST23). The brightness ratiodistribution data is indicated in FIG. 12 using a bar graph. Then, saidindividual light illumination aspect data including the brightness datain which the position and supply power are taken as parameters isproduced as the kind of table indicated in FIG. 16 by using, forexample, the least squares method to do the calculations (FIG. 15 stepST 24). As indicated in said FIG. 16, this individual light irradiationaspect data is correlated with a light irradiation unit identifier foridentifying each light irradiation unit 11, and is memorized and storedin an individual light irradiation aspect data memory unit D1 set up inmemory.

Next, the unit area division unit 37 divides said target area A intomultiple unit areas UA.

Concretely, as indicated schematically in FIG. 13, based on saidindividual light irradiation aspect data, the unit areas UA are set upby dividing said target area A so that the number or type of lightirradiation unit 11 irradiating light on each unit area UA differsrespectively, specifically, by dividing said target area A into everyarea where the overlap conditions differ (FIG. 15 step ST25).

Thereafter, the correspondence setting unit 38 sets up the correspondingmain light irradiation unit 11 for each unit area UA. Concretely, of thelight irradiation units 11 that irradiate light on a unit area UA, theone that provides the most light intensity is selected based on saidindividual light irradiation aspect data, and this is taken to be themain light irradiation unit 11 corresponding to the unit area UA inquestion (FIG. 15 step ST 26).

(2) Light Intensity Adjustment Operation

The light intensity adjustment operation is nearly the same as that ofsaid first embodiment, and therefore a flowchart and part of theexplanation will be omitted.

First, the photographic device 2 photographs the target area A, and thattarget area image is sent to the light intensity control unit 3 as imagesignals.

Meanwhile, based on the division results by said unit area division unit37, the image separation unit 31 separates said image signals into unitarea image signals for every unit area UA.

Next, the representative value calculation unit 32 calculates therepresentative value of the brightness (luminance level) of every unitarea image from these signals.

Thereafter, the comparison unit 33 compares the predetermined standardvalue of brightness (in this embodiment, the entire target area A is setto the same standard value) and said representative values of the unitarea images.

Then, based on these comparison results, the current control unit 34controls the current supplied to the corresponding main lightirradiation unit 11 so that the representative values approach saidstandard value. More concretely, taking said individual lightirradiation aspect data as the parameters, the current control unit 34outputs specifically by calculating the supply current from thebrightness at said central position obtained from this data such thatthe difference between the representative value and the standard valueenters within the permissible range.

This current control, for example, may be conducted all at once one timeonly, but when calculating the supply current, because this considersonly the change in brightness by the main light irradiation unit 11, anddoes not consider the effect of the adjacent light irradiation units 11that overlap, there is the risk that the results of calculating thedifference between the representative values and the standard value willnot be in the permissible range. In this case, these steps may berepeated until entering the permissible range.

(3) Scan Illumination Operation

After adjusting the light intensity of the light irradiation device 1 inthis way, specifically, after completing teaching, the light intensityof the light irradiation device 1 is fixed, and the surface scan of thework piece is conducted with that light intensity.

In this way, according to the present embodiment, even if slightdifferences are produced in the various light intensities andirradiation angles based on fluctuations of the product quality orassembly errors in the light irradiation units 11, because theindividual light irradiation aspects of the various light irradiationunits 11 on the target regions are pre-measured prior to controlling thelight intensity, and the various light irradiation units 11 arecontrolled by calculations corresponding to the individual lightirradiation aspects, not only is precise control possible, it is notnecessary to conduct control repeatedly until converging as with FBcontrol, and it is also possible to speed up the process.

Other Embodiments

Further, the present invention is not limited to the embodiment above,and a variety of forms is possible. In the explanation below, the samecodes are given to members corresponding to the previously describedembodiments.

For example, as indicated in FIG. 17, if multiple photographic devices 2are used to separate and photograph a target area A having a broadrange, adjacent photographic devices 2 may take photographs thatduplicate one part of said target region A. In this case, there is theproblem of which image from which photographic device 2 will be thebasis for light intensity control in the overlapping area. In this case,a priority ranking is given in advance to the photographic devices 2. Itis preferable that for the overlapping target region A, the lightintensity of said corresponding light irradiation unit 11 is controlledbased on the image obtained from the photographic device 2 with thehigher priority ranking, and for the target region A that thephotographic device 2 with the lower priority ranking photographs, thelight intensity of the light irradiation unit 11 corresponding to theother area is controlled taking the image of the previously describedoverlapping area as a standard.

Concretely, an explanation will be given by referring to FIG. 18 andFIG. 19.

FIG. 18 indicates the case when the highest priority ranking is grantedto the photographic device 2 positioned furthest to the end. In thiscase, first the light intensity control unit 3 controls the lightintensities of the corresponding light irradiation units 11 (concretely,light irradiation unit NO1, light irradiation unit NO2, and lightirradiation unit NO3 in the diagram) based on the image obtained by thephotographic device 2 in question. As a result, because the lightirradiation unit NO3 corresponding to the overlapping part is alsocontrolled, that light intensity is established. Next, the lightintensity control unit 3 controls the light intensities of thecorresponding light irradiation units 11 (concretely, light irradiationunit NO3, light irradiation unit NO4, and light irradiation unit NO5 inthe diagram) based on the image obtained by the adjacent photographicdevice with the second highest priority ranking. At this time, becausethe light intensity of the light irradiation unit NO3 has already beenestablished, this is not controlled, the image corresponding to thelight irradiation unit NO3 is taken as the standard, and the lightintensities of the light irradiation units 11 corresponding to the otherareas (concretely, light irradiation unit NO4, and light irradiationunit NO5 in the diagram) are controlled. If there is another adjacentphotographic device 2, that photographic device 2 has the next highestpriority ranking, and the successive light irradiation units 11 arecontrolled by the same procedure.

FIG. 19 indicates when the highest priority ranking is granted to thephotographic device 2 positioned in the center. In this case as well,first the light intensity control unit 3 controls the light intensitiesof the corresponding light irradiation units 11 (concretely, lightirradiation units NO3, NO4, and NO5 in the diagram) based on the imageobtained by the photographic device 2 in question. As a result, becausethe light irradiation units NO3 and NO5 corresponding to the overlappingpart are also controlled, those light intensities are established. Next,the light intensity control unit 3 controls the light intensities of thecorresponding light irradiation units 11 (concretely, light irradiationunits NO1, NO2, NO3, NO5, NO6, and NO7 in the diagram) based on theimages obtained by both of the adjacent photographic devices 2 with thesecond highest priority ranking. At this time, because the lightintensities of the light irradiation units NO3 and NO5 have already beenestablished, these are not controlled, the images corresponding to thoselight irradiation units NO3 and NO5 are taken as the standard, and thelight intensities of the light irradiation units 11 corresponding to theother areas (concretely, light irradiation units NO1, NO2, NO6, and NO7in the diagram) are controlled. If there is another adjacentphotographic device 2, that photographic device 2 has the next highestpriority ranking, and the successive light irradiation units 11 arecontrolled by the same procedure.

That is, if a photographic device 2 is set up with the highest priorityranking, then the priority rankings are set up in the order from theadjacent device, and the light intensity control is successivelyconducted in that order.

Consequently, when set up in this way, in addition to being able toestablish control of the light irradiation units 11 in regard tooverlapping areas, a mutually unified brightness image can be obtainedall at one time from the various photographic devices 2.

Meanwhile, if the images obtained by the various photographic devices donot need to be respectively unified, the corresponding light irradiationunits are respectively controlled independently based on the imagesobtained by the various photographic devices, and for the overlappingparts, the light intensity is controlled based only on the images bywhichever photographic device is predetermined, and the overlapping partof the images obtained by the other photographic device may be ignored.

Moreover, the light irradiation device may be provided with a lightintensity unevenness-mitigating member that mitigates light intensityunevenness dependent on gaps between adjacent light irradiation units.If, for example, a linear shaped light irradiation device is used, it ispreferable that this light intensity unevenness-mitigating member may bea lenticular lens having multiple concave grooves or convex ribsextending orthogonally to the direction of the line.

If the work piece is BATCH, etc., the present invention may be used onan area photographic device having light receiving elements such asCCDs, etc. arranged in a surface shape. In this case, a lightirradiation device (not indicated in the diagram) provided with multiplelight irradiation units lined up in a planar shape, or a lightirradiation device 1 like that indicated in FIG. 20 provided withmultiple light irradiation units 11 lined up in a partial concavespherical surface may be used. The target area A may be divided intounit areas UA like the divisions of the dotted lines in FIG. 21, forexample, for the former, or in FIG. 22, for example, for the latter.Further, a light diffuse plate, for example, may be cited as the lightintensity unevenness-mitigating member used in this case.

Of course, the present invention can be used in the same way even withwork pieces that are not translucent and scanning with reflectedillumination is utilized. There is no problem even if the lightirradiation device irradiates light by direct LEDs without passingthrough optical fibers.

Moreover, a more detailed light intensity control may be conducted bytaking LEDs or the light exit ends of optical fibers as the lightirradiation units respectively.

Further, the arrangement of the various parts that configure the lightintensity control unit may be freely modified, and these do not have tobe unified. For example, the power source and the current control unitof the light intensity control unit may be provided on the lightirradiation device side, and signal cables may transmit the comparisonresults signals from said comparison unit to the current control unit.If this is done, it is not necessary to use many thick power cables, andthe device can be made lighter. Of course, the various parts of thislight intensity control unit may be configured using digital or analogcircuits, and a computer and software may be used.

In addition, only the initial teaching regarding light intensity controlwas controlled in said embodiments, but, for example, control may beconducted intermittently, or light intensity control may be constantlyand continually conducted during the scan. If this is done, immediateresponses to changes in the work piece or to modification of machinetypes can be made, deterioration of illumination can be offset, andstable illumination is possible.

Further, when other light irradiation units other than the correspondinglight irradiation unit have an effect on the brightness of the unit areaimage, that effect may be taken into consideration and the other lightirradiation units may be controlled for additional brightness control ofthe unit area images. In this case, it is preferable to light the lightirradiation units one at a time in advance, and to measure the lightirradiation effect on the other unit areas.

Moreover, as indicated in FIG. 23, the LEDs 5 of the light irradiationdevice 1 may be directly installed in the casing 7, the optical fibers 6may be arranged inside of the casing. If this is done, it is notnecessary to run heavy fiber bundles comprising multiple optical fibersto the outside, therefore contributing to making the device lightweightand to improving ease of use. Further, in the same diagram, the boundarywall of each irradiation unit 11 may be eliminated to make aconfiguration that can obtain more uniform light.

The fewer the overlapping parts of the light irradiation range there arebased on the light irradiation units, the easier to control, but on theother hand, by providing light irradiation units lined up at anextremely narrow pitch, it is possible to control the distribution ofbrightness in an extremely smooth manner, for example, to heighten theuniformity of the brightness distribution by making many overlappingparts.

Further, in the second embodiment, brightness data included in theindividual light irradiation aspect data was memorized in tables thatmade the position, supply power, and light irradiation unit identifierthe parameters, but, for example, only the brightness data of thecentral position may be memorized by taking the supply power and lightirradiation unit identifier as parameters, and when controlling thelight intensity, the brightness data of the places separated from thecentral position may be taken as proportional to the brightnessdistribution data, and calculated every time.

In addition, the present invention is not limited to the examplesindicated in the diagrams above, and may be modified in a variety ofways within the range that does not deviate from that intent.

INDUSTRIAL APPLICABILITY

As described in detail above, according to the present invention, imagecompensation such as shading compensation, etc. by the image processorside is greatly reduced or made unnecessary, and therefore diminishingscan precision caused by image deterioration, etc. when compensating canbe prevented. In addition, shortening scan time and improving the scanprecision can be broadly promoted because the image processor canconcentrate on the image processing necessary for the original scan.

1. A light intensity adjustment system comprising: a light irradiationdevice that irradiates light on a predetermined target area set up on awork piece; a photographic device that photographs the target area andoutputs obtained target area images to an image processor for thepurpose of a surface scan, wherein said light irradiation device hasmultiple light irradiation units that are independently light intensityadjustable, and the light intensity adjustment system further comprisesa light intensity control unit that controls respective lightintensities of said light irradiation units so that brightness of thevarious parts of the target area images output by said photographicdevice approaches a predetermined standard value; and an individuallight irradiation aspect data acquisition unit, whereby lightirradiation aspects on said target area based on the light irradiatedfrom the individual light irradiation units are acquired in advance fromsaid target area images and are memorized in a predetermined memoryregion as individual light irradiation aspect data, and said lightintensity control unit controls the light intensities of said lightirradiation units based on said individual light irradiation aspectdata.
 2. The light intensity adjustment system according to claim 1,wherein said light intensity control unit controls the light intensitiesof the various light irradiation units to make the brightness of thevarious parts of said target area image uniform.
 3. The light intensityadjustment system according to claim 1, wherein said individual lightirradiation aspect data at least indicates a light irradiation range andbrightness distribution on the target area based on the various lightirradiation units supplied a predetermined power.
 4. The light intensityadjustment system according to claim 1, configured so that said targetarea is divided into multiple unit areas, each unit area corresponds toone light irradiation unit that mainly irradiate the unit area, and thelight irradiation unit is taken as the main light irradiation unit ofthe unit area.
 5. The light intensity adjustment system according toclaim 4 configured so that said unit areas and the light irradiationunits are given a one to one correspondence.
 6. The light intensityadjustment system according to claim 4, wherein, based on the lightirradiation range of each light irradiation unit that said individuallight irradiation aspect data indicates, said target area is dividedinto multiple unit areas so that the number or type of light irradiationunit that irradiates light on the various unit areas differrespectively.
 7. The light intensity adjustment system according toclaim 6, wherein, based on the brightness distribution of each lightirradiation unit that said individual light irradiation aspect dataindicates, for each unit area, the light irradiation unit that gives thegreatest light intensity is taken as the main light irradiation unit ofthe unit area.
 8. The light intensity adjustment system according toclaim 4, wherein said light intensity control unit comprises an imageseparation unit that separates said target area image into images ofsaid various unit areas, a representative value calculation unit thatcalculates a representative value of the brightness of the various unitarea images, a comparison unit that compares a predetermined standardvalue of the brightness and the representative value of said each unitarea image, and a unit light intensity control unit that controls thelight intensity of the main light irradiation unit corresponding to theunit area so that each representative value approaches said standardvalue based on comparison results by said comparison unit.
 9. The lightintensity adjustment system according to claim 8, wherein saidrepresentative value calculation unit calculates the mean brightness ofthe unit area image and takes the value as the representative value. 10.The light intensity adjustment system according to claim 1, wherein thelight irradiation device comprises light irradiation units lined up in alinear or surface shape.
 11. The light intensity adjustment systemaccording to claim 10, wherein the light irradiation device comprises alight intensity unevenness-mitigating member that mitigates unevennessof light intensity dependent on gaps between adjacent light irradiationunits.
 12. The light intensity adjustment system according to claim 1,comprising multiple photographic devices, wherein the photographicdevices photograph by separating said target area, and if eitheradjacent photographic device photographs by duplicating a part of saidtarget area, for the overlapping target area, the light intensity of thecorresponding light irradiation unit is controlled based on the imageobtained by the photographic device with the higher priority ranking,and for the target region that the photographic device with a lowerpriority ranking photographs, the light intensity of the lightirradiation unit corresponding to that other area is controlled takingsaid image of the overlapping target area as the standard.
 13. A lightintensity adjustment system comprising: a light irradiation device thathas multiple light irradiation units that are independently lightintensity adjustable and that irradiates light toward predeterminedtarget areas; a photographic device that photographs said target areasthrough a lens and outputs target area images as being photographedimages; a light intensity control unit that controls the respectivelight intensities of said light irradiation units so that the brightnessof each part of the target area images that said photographic device hasoutput approaches a predetermined standard value; and an individuallight irradiation aspect data acquisition unit, whereby lightirradiation aspects on said target area based on the light irradiatedfrom the individual light irradiation units are acquired in advance fromsaid target area images and are memorized in a predetermined memoryregion as individual light irradiation aspect data, and said lightintensity control unit controls the light intensities of said lightirradiation units based on said individual light irradiation aspectdata.
 14. A light intensity adjustment system comprising: a lightirradiation device that irradiates light on a predetermined target areaset up on a work piece; and a photographic device that photographs thetarget area and outputs obtained target area images to an imageprocessor for the purpose of a surface scan, wherein said lightirradiation device has multiple light irradiation units that areindependently light intensity adjustable, and the light intensityadjustment system further comprises a light intensity control unit thatcontrols respective light intensities of said light irradiation units sothat brightness of the various parts of the target area images output bysaid photographic device approaches a predetermined standard value,wherein the light irradiation device comprises a light intensityunevenness-mitigating member that mitigates unevenness of lightintensity dependent on gaps between adjacent light irradiation units.